Most major chronic conditions are related to patient environment and lifestyle factors that act on preexisting genetic dispositions to diseases. This is true of many cancers, hypertension, heart disease, diabetes, and mental illnesses. Ways to prevent or reduce the severity of such diseases include changing a patient's environment and/or lifestyle (e.g. diet, exercise, stress, substance abuse, pollution) or by following therapeutic regimes that lessen the impact of environment or lifestyle (e.g. taking cholesterol lowering drugs).
One of the difficulties in changing patient behavior is that a prognosis based on lifestyle factors is very imprecise and it is easy for a patient to rationalize why such a prognosis does not apply to him or her, or at least not yet. Everyone knows an example of someone who smoked and drank and lived to a ripe old age. Everyone also knows of someone who was health-conscious and jogged every day, yet died of a heart attack. Because a prognosis is vague and difficult to individualize to a patient, many patients do not change their behavior until it is too late.
A major advance in preventative medicine is the ability to test for a genetic predisposition for certain diseases. Unfortunately, the human genome is incredibly complex and based on a gene sequence alone, there are still too many degrees of freedom to make an accurate and personalized prognosis for an individual patient. This is especially true for genetic diseases that are heavily influenced by environmental and lifestyle factors.
In order to use genotypes for disease prevention, it is necessary to. develop better methods for profiling a patient's phenotype in order to reduce the degrees of freedom and provide a more accurate prognosis. It may also be necessary to continue to profile the patient over time in order to monitor behavior and adjust the prognosis. In addition, it is hoped a patient will be more motivated to adhere to a prescribed treatment or regimen if he or she can easily see the effects of changes in behavior.
Diseases that are not caused by genetic factors are often caused by pathogens. Many virus-induced diseases such as hepatitis, AIDS, and herpes are incurable in part because of the high mutation rate of the pathogens. Vaccines created to combat such pathogens are quickly rendered ineffective.
With the recent advances in biotechnology, it is now possible to sequence genes to create a genetic profile of an organism. Thus it is possible to determine the specific genetic makeup of a pathogen in a patient, and to use that information to create a patient-specific treatment or vaccine.
Unfortunately, because genomes are so complex and because the patient phenotype upon which the pathogen acts is so variable, there are too many degrees of freedom to tailor a precise treatment to a patient's need. In order to use pathogen genotypes in treatment of disease, it is necessary to develop better methods of profiling a patient's phenotype in order to reduce the degrees of freedom and provide a more accurate prognosis. It may also be necessary to monitor the patient over time in order to determine the effectiveness of the treatment and to adjust the treatment to the patient's response.
All of these approaches are very cost-intensive since they are predicated on collecting patient-specific genotype and phenotype data. Using traditional data collection methods, in view of the rapidly growing genotype knowledge, is therefore inadequate.